Transformation Capability Optimization and Product Application Potential of Proteatia brevitarsis (Coleoptera: Cetoniidae) Larvae on Cotton Stalks

SIMPLE SUMMARY: The Xinjiang Uyghur autonomous region is the most important area for cotton production in China, where recycling of cotton stalks (CS) as a useful resource should be encouraged. This article investigated the technical feasibility of CS as a feed and fertilizer based on the transformation of P. brevitarsis larvae. Decomposition inoculant, fermentation duration, and cattle manure ratio were considered the key factors affecting the transformation capability of P. brevitarsis larvae on CS. The research showed that 40–50% of cattle manure, 0.1% VT inoculant, and a fermentation duration of 25–30 days were the optimal technical parameters. The protein content of the larval body was as high as 52.49%, and the fat content was 11.7%. The organic matter content of frass (larvae dung-sand) was 54.8%, and the content of total nitrogen, phosphorus, and potassium (TNPK) was 9.04%, which is twice more than that of the organic fertilizer standard (NY525-2021, Beijing, China, TNPK ≥ 4.0%). The application of CS as feed (larval body) and fertilizer (larvae dung-sand) is feasible, promoting the utilization of both CS and cattle manure. ABSTRACT: Cotton stalks (CS) are a potential agricultural biomass resource. We investigated the use of CS as a feed for Proteatia brevitarsis Lewis larvae and the resulting frass (larvae dung-sand) as a fertilizer. Based on a three-factor experiment (decomposition inoculant, fermentation duration, and cattle manure ratio), the optimal parameters for the transformation of CS using P. brevitarsis larvae were determined as 40–50% of cattle manure, the use of VT inoculant and a fermentation duration of 25–30 days. Regarding the products of the transformation, the protein content of the larval body was as high as 52.49%, and the fat content was 11.7%, which is a suitable-quality insect protein source. The organic matter content of larvae dung-sand was 54.8%, and the content of total nitrogen, phosphorus, and potassium (TNPK) was 9.04%, which is twice more than that of the organic fertilizer standard (NY525-2021, Beijing, China, TNPK ≥ 4.0%), and larvae dung-sand has the potential of fertilizer application. Therefore, CS as a feed and fertilizer based on the transformation of P. brevitarsis larvae is feasible, and it is a highly efficient way to promote the utilization of both CS and cattle manure.